221 - Targeting HDAC2 protects monocytes against metabolic stress-induced priming and dysfunction

Abstract

Background Monocytes priming and reprogramming induced by metabolic stress is mediated by protein S-glutathionylation and is prevented by overexpression of glutaredoxin 1 (Grx1). Here we tested the hypothesis that inhibition of HDAC2 prevents monocyte dysfunction by inducing Grx1 and preventing metabolic stress-induced protein S-glutathionylation. Methods THP-1 monocytes were incubated with the HDAC inhibitor Scriptaid for up to 72 h and the expression of Grx1, HDAC2 and s-actin, as well as the level of acetylation lysine 9 on H3 (H3K9Ac), were examined by Western blotting. To identify the specific HDAC involved in Grx1 regulation, we used small interfering RNA to knockdown targeting HDAC1, 2 and 3. Bone marrow-derived macrophages (BMDM) were generated from LysMcre+/-HDAC2+/- and LysMcre+/- mice and primed with LDL (100 μg/ml) plus high glucose (25 mM) for 36 h. HDAC2 mRNA levels were quantified by qRT-PCR. Macrophage priming was assessed using the MKP-1 activity assay. Results Scriptaid increased Grx1 protein expression in THP-1 monocytes 1.8-fold after 36 h increased acetylation of H3K9 1.5-fold. Scriptaid also rescued MKP-1 activity and normalized chemotactic activity in primed THP-1 monocytes. Induction of Grx1 was only observed in cells treated with anti-HDAC2 siRNA (1.5-fold increase) but no changes were observed in response to either HDAC1 or HDAC3 knockdown. Grx1 mRNA levels in blood monocytes from HDAC2 deficient mice were 20-fold higher than in monocytes from control mice. BMDM from LysMcre+/-HDAC2+/- mice showed higher MKP-1 activity and Grx1 protein expression than BMDM from LysMCre+/- mice. Furthermore, MKP-1 activity was inhibited by metabolic stress in control BMDM but was maintained in BMDM from LysMCreHDAC2+/- mice. Conclusions Grx1 expression in blood monocytes and monocyte-derived macrophages is regulated by HDAC2. Inhibition of HDAC2 induces Grx1 and protects monocytes from metabolic stress-induced dysfunction, making HDAC2 a novel therapeutic target for chronic inflammatory diseases associated with metabolic disorders.